Known substance classes of porous solids are called metal organic frameworks (MOF) or coordination polymers. The theory of coordination bonds developed by Alfred Werner [A. Werner, Z. Anorg. Allg. Chem. 3 (1893) 267] made it possible for the first time to understand the experimental results of complex inorganic chemistry. Stable coordination polymers are obtained by adding organic molecules capable of complex formation, like diamines or diacids, to dissolved inorganic salts. The distances between the metal ions as coordination centers can be set in a wide range through the structure, in particular of the organic components, and result in micro- to mesoporous substances. Coordination polymers can thus be varied and are substantially documented [S. Kitagawa, et al. Angew. Chem. Int. Ed. 43 (2004) 2334].
The ability to synthesize coordination polymers with porosity results in a new class of materials that are crystalline molecular sieves. The atomic structure of any coordination polymers can be determined by x-ray crystallography, the dimensions of the pores or channels can be determined with excellent certainty. The internal surface areas of some porous coordination polymers are significantly greater than other porous materials. The pore sizes/shapes are highly tunable and large pore sizes can be synthesized when compared to know zeolites. Functionalization of the backbones or frameworks in these materials can be achieved by starting the synthesis with organic linkers with functional groups already installed or by post synthesis modification.
Recently, the coordination copolymerization method with two topologically distinct linkers was reported, and can give rise to a microporous coordination polymer (MCP) with a previously unattainable mesoporous structure [K. Koh, A. G. Wong-Foy and A. J. Matzger, Angew. Chem., Int. Ed., 47, (2008), 677]. The first example of this strategy, UMCM-1 (University of Michigan Crystalline Materials), illustrated that instead of a mixture of crystalline phases arising from the independent assembly of a single linker type, a novel phase incorporating all organic components can be produced by controlling the mole ratio of each organic linker.